Following are the various technologies embedded in our proprietary computer codes (A: ATENA; M: Merlin).

Finite Element

• Nonlinear analysis (A-M)
• Algorithms: Newton-Raphson, Secant Newton, Initial Stiffness, Line Search, Arc-Length.
• Time Integration: Implicit (Newmark, Hughes); Explicit (single CPU/Parallel) (A-M).
• Rich libraries of constitutive models for concrete and steel (A-M)
• Embedded or discrete modeling of reinforcement (A-M)
• Static and Dynamic analysis with restart capabilities (A-M)
• Discrete Cracks/interfaces: Over 5 different types of interface elements. (A-M)
• Smeared crack elements. (A-M)
• Reservoir Modeling: Added mass or fluid elements (M)
• Uplift models: Automatic adjustment with crack propagation; Static (FERC) or dynamic uplift (M).
• Scalar Field Problems: Thermal (transient) steady state diffusion analyses. (A-M)
• Staged construction/excavation approximated (A-M).

Seismic Analysis

• Probabilistic Seismic Hazard Analysis (site specific ground motion selection and scaling).
• Real vs Synthetic ground motions.
• Different dynamic analyses techniques (IDA: Incremental Dynamic Analysis; CLA; CLoud Analysis; MSA: Multiple Strip Analyses; ETA: Endurance Time Analyses; POA: Push Over Analysis).
• Selection of optimal intensity measure parameters (sufficiency, efficiency, practicality and Hazard Compatibility).
• Rayleigh Damping: Different coefficients for rock and concrete.
• Radiation damping: Without/with interaction with free field (Lysmer/Miura).
• Ground Motion deconvolution.

Fracture Mechanics

• LEFM (Linear Elastic Fracture Mechanics): 2D and 3D Calculation of stress intensity factors using singular element, or J Integrals.
• EPFM (Elasto-Plastic Fracture Mechanics): J1 and J2 integral calculation.
• Cohesive crack model based on an extension of Hillerborg’s model.
• Fatigue crack propagation with automatic crack propagation.

ASR

Based on Saouma-Perotti model:

• Temperature and relative humidity dependent.
• Material kinetic (expansion vs time) specified.
• Anisotropic expansion accounted for (through expansion redistribution).
• Material degradation.
• Time integration.
• Coupled with automated System Identification ot obtain material parameters from FEA and in-situ irreversible measurements (displacement).
• Can be coupled with subsequent hazard load (hydrological or seismic).
• Fully validated with RILEM Benchmark problems.
• Extensively used for dam, NCS, bridges, walls.

Risk, Reliability, and Resilience

• Seismic and hydrologic fragility functions.
• Time-dependent (aging) reliability assessment
• Determination of rare probability of failure
• Vulnerability assessment and estimation of loss of life, money and downtime
• Risk-based and risk-informed assessment of infra-structures
• Life cycle and resilience evaluation of structures and communities
• Developing dam and nuclear safety management program
• Assessing portfolio of dams and NPPs

Soft Computing

• Advanced data sampling techniques (Monte Carlo, Latin Hypercube, Importance Sampling, Sobol, Halton) with potential correlation
• Accounting for both epistemic and aleatory uncertainties
• Sensitivity analysis, Tornado diagram, and important random variables
• Uncertainty quantification and developing probability-based response
• Machine Learning and matrix completion techniques (neural network, support vector machine, polynomial Chaos expansion, etc.)
• Application of HDMR (high-dimensional data reduction) techniques
• Developing response surface meta-models for generalized applications